Emigration, exposure and bilingualism.

[roddy]

The best plan in terms of developing language skills might be to finishing elementary in the first language environment, secondary school and college in the second language environment while continuing to study the first language at home, and then return to the first language environment for further education and work

I agree with what Gato says here, but I also note everyone I've met who has done this has complained or commented to some degree about the effects - maybe just joked along the lines of 'and so now I don't fit in anywhere', to becoming genuinely unhappy when they attempt to move back 'home'.

All depends how it's done, and I can of course see the linguistic and perhaps educational advantages.

[Glenn]

Probably depends on the person and the environment they came up in, too.

[Guest realmayo]

Out of interest, you can be perfectly fluent but still have an accent, right?

[gato]

Yes, like Henry Kissinger and Ariana Huffington.

[Guest realmayo]

Well, a thick accent impedes your understanding (or ease of understanding) of the speaker -- clearly not desirable. But I can think of people with fluent English, as easy to understand as any native speaker, but who are obviously German, or French.